137 lines
3.8 KiB
C
137 lines
3.8 KiB
C
#include <stdlib.h>
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#include "mpg123.h"
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int tabsel_123[2][3][16] = {
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{ {0,32,64,96,128,160,192,224,256,288,320,352,384,416,448,},
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{0,32,48,56, 64, 80, 96,112,128,160,192,224,256,320,384,},
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{0,32,40,48, 56, 64, 80, 96,112,128,160,192,224,256,320,} },
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{ {0,32,48,56,64,80,96,112,128,144,160,176,192,224,256,},
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{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,},
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{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,} }
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};
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long freqs[9] = { 44100, 48000, 32000,
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22050, 24000, 16000 ,
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11025 , 12000 , 8000 };
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#define HDRCMPMASK 0xfffffd00
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struct bitstream_info bsi;
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int ssize;
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unsigned long read_header(BYTE *mpeg)
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{ unsigned long hdr;
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hdr = *mpeg++;
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hdr <<= 8;
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hdr |= *mpeg++;
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hdr <<= 8;
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hdr |= *mpeg++;
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hdr <<= 8;
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hdr |= *mpeg++;
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return hdr;
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};
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int head_check(unsigned long head)
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{
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if( (head & 0xffe00000) != 0xffe00000)
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return FALSE;
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if(!((head>>17)&3))
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return FALSE;
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if( ((head>>12)&0xf) == 0xf)
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return FALSE;
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if( ((head>>10)&0x3) == 0x3 )
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return FALSE;
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return TRUE;
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}
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int decode_header(struct frame *fr,unsigned long newhead)
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{
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if( newhead & (1<<20) ) {
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fr->lsf = (newhead & (1<<19)) ? 0x0 : 0x1;
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fr->mpeg25 = 0;
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}
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else {
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fr->lsf = 1;
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fr->mpeg25 = 1;
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}
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fr->lay = 4-((newhead>>17)&3);
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if( ((newhead>>10)&0x3) == 0x3) {
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fprintf(stderr,"Stream error, reserved sampling rate\n");
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return 0;
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}
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if(fr->mpeg25) {
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fr->sampling_frequency = 6 + ((newhead>>10)&0x3);
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}
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else
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fr->sampling_frequency = ((newhead>>10)&0x3) + (fr->lsf*3);
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fr->error_protection = ((newhead>>16)&0x1)^0x1;
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if(fr->mpeg25) /* allow Bitrate change for 2.5 ... */
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fr->bitrate_index = ((newhead>>12)&0xf);
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fr->bitrate_index = ((newhead>>12)&0xf);
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fr->padding = ((newhead>>9)&0x1);
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fr->extension = ((newhead>>8)&0x1);
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fr->mode = ((newhead>>6)&0x3);
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fr->mode_ext = ((newhead>>4)&0x3);
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fr->copyright = ((newhead>>3)&0x1);
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fr->original = ((newhead>>2)&0x1);
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fr->emphasis = newhead & 0x3;
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fr->stereo = (fr->mode == MPG_MD_MONO) ? 1 : 2;
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if(!fr->bitrate_index)
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{
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fprintf(stderr, "Stream error, free format bitrate index not supported\n");
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return 0;
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}
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switch(fr->lay)
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{
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case 1:
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fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ?
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(fr->mode_ext<<2)+4 : 32;
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fr->framesize = (long) tabsel_123[fr->lsf][0][fr->bitrate_index] * 12000;
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fr->framesize /= freqs[fr->sampling_frequency];
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fr->framesize = ((fr->framesize+fr->padding)<<2)-4;
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break;
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case 2:
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fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ?
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(fr->mode_ext<<2)+4 : fr->II_sblimit;
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fr->framesize = (long) tabsel_123[fr->lsf][1][fr->bitrate_index] * 144000;
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fr->framesize /= freqs[fr->sampling_frequency];
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fr->framesize += fr->padding - 4;
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break;
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case 3:
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fr->do_layer = do_layer3;
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if(fr->lsf)
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ssize = (fr->stereo == 1) ? 9 : 17;
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else
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ssize = (fr->stereo == 1) ? 17 : 32;
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if(fr->error_protection)
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ssize += 2;
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fr->framesize = (long) tabsel_123[fr->lsf][2][fr->bitrate_index] * 144000;
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fr->framesize /= freqs[fr->sampling_frequency]<<(fr->lsf);
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fr->framesize = fr->framesize + fr->padding - 4;
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break;
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default:
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return (0);
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}
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return 1;
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}
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//void set_pointer(long backstep)
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//{
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// bsi.wordpointer = bsbuf + ssize - backstep;
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// if (backstep)
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// memcpy(bsi.wordpointer,bsbufold+fsizeold-backstep,backstep);
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// bsi.bitindex = 0;
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//}
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